1. Field of the Invention
The present invention relates to a catalyst which is suitable for selectively converting hydrocarbons in a hydrotreating process. More particularly, the invention relates to catalysts suitable for hydrodesulfurizing and/or hydrodenitrogenizing hydrocarbons while simultaneously cracking them.
2. Background
It is known that to enhance cracking activity such catalysts may contain an alumina-silica-alumina carrier built up from alumina and amorphous silica-alumina, on which there have been provided hydrogenation metals, e.g., molybdenum, nickel, and/or cobalt. Such catalysts are described in U.S. Pat. No. 4,238,316, which discloses catalysts containing 10-60 wt. % of alumina derived from boehmite or a mixture of boehmite and amorphous hydrous alumina and 40-90 wt. % of amorphous silica-alumina. In addition such catalysts may contain a small quantity of hydrogenation metals, e.g., tungsten, molybdenum, and nickel. This patent specification advises against the use of boron in such a quantity as might affect the catalytic conversion.
Alumina-silica-alumina-containing catalysts also can be employed to improve selectivity in hydrocarbon hydrotreating processes. Such is described in U.S. Pat. No. 4,062,809, which discloses the preparation of catalysts by mixing an alumina matrix with a silica-alumina cogel and adding thereto such hydrogenation metals as molybdenum, tungsten, nickel, and cobalt. Said catalysts display high selectivity, in particular when converting heavy oils into middle distillates.